Distillation of alcohols from aqueous mixtures of alkyl sulfates and sulfuric acid



Patented May 17, 1949 DIsTmLA'rIoN oFALcorloLs FnoM AQUE- S MIXTUBES FALKYL SULFATES AND 0U SULFURIC ACID Francis M. Archibald, Elizabeth, N.J., assigner,

by mesne assignments, lto Standard 0il Development Company, acorporation o! Delaware Application Ncvein'lier ls', 1044, serial Nc.563,745

(cl. 2oz-57i l 6 Claims. This invention relates to the production ofalcohols from oleilns occurring in cracked petrohol from an acidextract.

In the manufacture of alcohols from various olenic materials, the olensare absorbed in sulfuric acid to form alkyl esters which remain in theacid as an acid extract. The extract is then diluted with water tohydrolyze the esters to the corresponding alcohols which are recoveredhydrocarbon feedstock consisting primarily ci a lleum material, and vitrelates more particularly to Y a method for more eiectively distillingthe alcoby heating in a packed or plate column usually l countercurrentto a stream of steam. During the distillation step, the heat of thesteam tends to form polymers and freecarbon which accumulate in thepacking or on the plates of the column and cause foaming, stoppages. andineiiicient opera.- tion. Cleaning of the stills after shut down istedious and is a time consuming operation and in some cases requires theuse of expensive solvents to break up the tarry and rcsinous massformed. Furthermore, much of the polymeric material remains in thediluted acid and upon reconcentration of the acid to its formerstrength, the polymers are carbonized and precipitate upon subsequentdilution when re-used in the process.

It is therefore one object of this invention to C4 hydrocarbon fractioncontaining 15-80% butenes is introduced into the bottom of agitator I,through line 2. Sulfuric acid of about 80-90% strength is introduced byline 3 into the top of agitator I. The agitator is preferably maintainedat a temperature between and 50 C. by means of refrigeration coil 4 andthe contents are thoroilghly mixedfby means oi agitator blade- 5, so asto form an acid extract containing monobutyl and dibutyl sulfates whichis removed from the bottom of agitator I through line 6, and introducedinto settler 1 where unreacted butenes and other hydrocarbons` areremoved through line 8. Acid extract is removed from settler 8 throughline 9 and diluted with water introduced through line Ill and passedthrough oriilce II into hydroprevent the deposit of such polymeric,tarry and carbonaceous material in the still during the distillation' ofthe alcohol from the extract.

It is a still further object of this invention to provide a process forthe production of alcohols from acid extracts in a continuous mannerwithout any periodic shutdown to clean out the still.

Other objects and a further understanding of this invention may be hadby referring to the following description and claims taken inconjunction with the accompanying drawing which is a diagrammatical viewof the general ilow plan of the process;

According to the present invention, the above objects are accomplishedby adding a small amount of a non-volatile hydrocarbon oil to the lyzerI2. The mixture of acid extract and water is passed throughv hydrolyzerI2 at a sufciently slow rate so that the dialkyl esters and most of themono alkyl esters are substantially completely `converted into alcohol.The hydrolyzed extract is removed from the hydrolyzer through line I3,diluted with water from line I4 to an acid concentration of andintroduced into stripper I6 through line il at a temperature of about 75C. In stripper I6 butyl alcohol is stripped from the hydrolyzate bymeans of a countercurrent stream of steam introduced through line i'Iand passed through line 20 to crude alcohol storage` for nishing.

During this stripping operation, a portion of the olefins obtained fromthe acid. extract are polymerized to solid materials and partiallydecomposedto carbonaceous tars which tend to plug up the lpacking of thecolumn. According to this invention, the deposition of this polymericand carbonaceous material in the stripping column is prevented byadding'a non-volatile petroleum oil to the stl'ipper. This oil ispreferably introduced near the middle of the column through line I9. Theaddition oi.' oil at this point results in dispersi'ng the tal', polymerand carbon in the oil and keeping the plates or packing of the columnclean. Acid extract, of approximately 45% concentration containing theoil added through line I9 is removed from the bottom of stripper I6 andintroduced into settler 22 by line 2|. The acid is allowed to standuntil alayer of oil containing polymeric material and carbonaceousmaterial separates out. This oil layer is removed through iline 23;Clean spent acid is removed from the'settler through line 125 and passedto reconcentrator 24 where it 'is 'heated by indirect heat exchange witha high boiling material such as diphenyl or a mixture of diphenyl anddiphenyl oxide. Reconcentrated acid is removed from the reconcentrator24 by means of line 3 and recycled to agitator I for use as theabsorption medium therein.

From the above description it is clear that a process has been foundwhereby the detrimental effects due to the polymerization and decomposi-1 tion occurring in olen extracts during distillation of the alcoholtherefrom has been overcome by the introduction of a non-volatilehydrocarbon oil into the distillation column in which the alcohol isstripped from the extract. While any nonvolatile oil can be used forthis purpose, it is preferable to use an oil having a Saybolt Unlversalviscosity of 100 at 100 F. prepared from a naphthenic base crude.

C4 cut from agitator I. A suitable oil may also be obtained from thespent acid removed from stripper I6. A certain amount of oil is alwaysproduced and can be skimmed from the spent acid and separated from-tarby ltering or distillation. The oil may be added in amounts of about 2%of the material feed to the column for a period of one half hour everytwenty-four hours. However, it is preferable to continuously feed .05 ofoil based on the feed to the column. For example, during the preparationof butyl alcohol as described above, it was found that the addition ofabout 2% of oil tothe stripping column effectively prevented clogging ofthe plates and diiculties due to such shutdowns were completely avoided.

While the above process has been described in connection with theproduction otbutyl alcohol, this is by way of illustration only, and itis not intended to be limiting since the process is applicable to thepreparation of other alcohols such as ethyl alcohol, isopropyl alcoholand higher alcohols. such as amyl alcohol.

The nature and objects of the present invention, having thus been setforth and the specic l examples of the same given what is claimed as newand useful and desired to be secured by Letters Patents is:

' 1. In a process for recovering alcohol from an aqueous mixture ofalkyl sulfates and sulfuric acid, in which the acid has a concentrationof about 45%, by distillation of the mixture to remove alcohol therefromand wherein polymers, tars, and free carbon are formed as a result ofthe distillation, the improvement which comprises carrying out suchdistillation in the presence of a small amount of a hydrocarbon oil 4which is non-volatile under the distillation conditions and which isafiux for the polymers, carbon,

tars, etc.

For example, a suitable oil is that obtained by distilling the spent 2.The improvement according to claim 1`, in which the non-volatilehydrocarbon oil is added to the aqueous mixture during the distillationstep in the amount of about 2% of the aqueous mixture fed to such stepfor a period of one half hour every twenty-four hours.

3. The improvement according to claim 1, in which the non-volatilehydrocarbon oil is added to the aqueous mixture continuously during thedistillation step, in the amount of about 0.05% of the mixture fed tosuch step.

4. The improvement according to claim 1, in which the non-volatilehydrocarbon oil is a naphthenic base oil having a Saybolt Universal viscosity of about at 100 F.

5. In a process for recovering alcohol from an aqueous`mixture of alkylsulfates and sulfuric acid, in which mixture the acid has aconcentration of about 45%, by distillation of the mixture in adistillation zone from which alcohol is removed overhead and spent acidfrom the bottom of the zone and wherein polymers, tars, and free carbonare formed as a result of the distillation, the improvement whichcomprises adding to the aqueous mixture fed into said distillation zonea hydrocarbon oil which is non-volatile under the distillationconditions and which is a ux for the polymers, carbon, and tars, wherebythese distillation decomposition products are dispersed and dissolved inthe oil, withdrawing the oil from the bottom of the distillation zonewith -the spent acid, separating the non-volatile oil and decompositionproducts from the spent acid, and reconcentrating said acid.

6. The improvement according to claim 5', in which said non-volatilehydrocarbon oil is added to the aqueous mixture during the distillationstep. and at a point below the middle of the distillation zone.

FRANCIS M. ARCHIBALD.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,954,506 Van Peski et al Apr.10, 1934 2,006,400 Lorang et al July 2, 1935v 2,107,265 Archibald Feb.8, 1938 2,286,503 Ocon June 16, 1942 2,324,955 Rupp et a1 July 20, 1943

